Mythbusters Part 3: Recycling our Non-Toxic Battery Packs

Kurt Kelty11 mars 2008

As I make presentations at various conferences regarding our battery pack, or Energy Storage System (ESS), I’m often asked the question ”Isn’t the battery pack toxic” and whether or not it can be disposed of safely. To reach a wider audience, I thought it best to address these questions in our blog.

Energy Storage System

First, it’s necessary to understand the contents of our ESS. The cells in our battery are composed mainly of lithium metal oxides. They are manufactured in Japan, a country with very strict environmental laws. Emissions and effluents are strictly controlled and monitored. The cells meet the requirements set forth by the Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment 2002/95/EC (commonly referred to as the Restriction of Hazardous Substances Directive or RoHS). In other words, they do not contain any of the following:

Lead

Mercury

Cadmium

Hexavalent chromium (chromium xxx or Cr6+)

Polybrominated biphenyls (PBB)

Polybrominated diphenyl ether (PBDE)

Above and beyond RoHS, our lithium ion cells contain no heavy metals, nor any toxic materials. In fact, our cells and ESS, by law, could be disposed of by putting them in a landfill. However, we have no intention of landfilling our ESS.

There are some exciting potential uses for the ESS in its afterlife. While our ESS is designed to maximize performance and life in our roadster, at some unfortunate point, the ESS will come to the end of its useful life in the application :(. However, it might be possible to use the ESS in other applications. For example, the ESS could be used as a power source for off-grid backup or load leveling. The battery requirements for such an application are not as demanding as a high performance vehicle battery. This being said, eventually the batteries will no longer hold a significant charge and will need to be disposed of.

minimize energy consumption utilized during the transportation and recycling process;

To understand how we attain these goals, you first need to understand a few basics about our ESS construction. The ESS is comprised of 11 modules. These 4.8kWh modules are made up of plastics, aluminum, copper, some electronics and lots of other confidential stuff to improve safety and performance. Each of the roughly 35kg modules is inserted into an aluminum enclosure as shown above.

The enclosure also contains our 12V power supply, a battery system management board and other safety stuff. Aside from the cells, most components in our ESS are designed to last the life of the car. If an individual ESS reaches its end of life, we plan to replace the modules, not the whole ESS. To retrieve the used modules from the market, Tesla will set up an exchange program in which customers receive a credit when they return their modules.

The recycling process follows the below steps:

The ESS is discharged for safety reasons

The Propylene glycol in the cooling tubes is drained and recycled locally

The electronics are removed and tested to determine if they can be reused

The wires and some other metals are removed and recycled locally

The modules are stored until the quantity is large enough to justify a stop on the “milk run” by the KBI truck (this semi truck makes regular runs from their facility in Los Angeles to their recycling facility in Trail, British Columbia, Canada).

Upon arrival at Toxco’s facility in Trail, the excitement begins (if you’re into hardcore destruction). The modules are frozen in liquid nitrogen to prevent further reactions of the lithium components.

The modules are put into a shredder with mammoth teeth and broken into chunks less than 2” long (tiny sparks appear, but otherwise it’s surprisingly not that exciting).

The small chunks are fed into the hammer mill (don’t you love these names?) as pictured below to pulverize the remaining chunks into even smaller pieces.

Hammer mill

Screens then separate the materials into three different products:

fluff

copper cobalt

slurry

The fluff, pictured above, is trucked back to the U.S. border and properly disposed. This mostly contains plastic.

The copper cobalt product is shown on left. The cobalt filter cake is shown on the right.

The copper cobalt product is sold for recovery of metals such as cobalt, aluminum, nickel, and copper. The slurry is processed into a cobalt filter cake. This cake is then reused in appliance coatings.

Soda ash is added to resulting process solution and precipitates out as lithium carbonate; liquid is bled off after lithium salt recovery, and is sent off as non hazardous effluent for proper disposal.

As you can see, the recycling process is mainly a mechanical and chemical one. It does not involve any smelters; so emissions are kept to a minimum.

The result from this process is that we are able to recycle about 60% of the ESS materials and reuse a further 10% (by weight). We currently plan to landfill only the benign fluff, which comprises about 25% of the ESS, but we expect to nearly eliminate this in the future when our volumes get higher and we can justify the effort required to separate and reuse the plastic.

Keep in mind that we have only done a few trial runs with our modules. We’re hoping that we won’t need to recycle our modules for many years to come. However, we believe it is important, before we start shipping cars, to understand and plan for the eventual disposal of these vehicles.